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QuantumDot
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[*] posted on 20-8-2020 at 08:32
Nickel chloride?


So over the past week I've been experimenting with making nickel(II) chloride by dissolving fine nickel powder in 30% HCl with some haphazard additions of 30% H2O2 to speed it up. I got to a nice emerald green solution and once all the powder had disappeared, I stopped additions. I then went to boil off the water to leave behind the beautiful lime green crystals.

What happened instead was I stupidly left the hotplate unattended and the beaker evaporated to dryness. What was left behind is the yellow-brown flakes in the first photo. Around the desk were spots of green, which I assume is the hexahydrate. I collected them and dissolved them in a little distilled water, and got a cyan solution pretty quickly. When I attempted to dissolve the yellow flakes I instead got an opaque brown solution.

So my questions are:
Should I throw away the beaker I used?
What is the yellow/brown flaky stuff?
If it's nickel chloride dihydrate, why didn't it dissolve?
Is it an oxide, despite being yellow?

Guesses, wild or educated, are welcome.
Flakes.jpg - 811kB Mud.jpg - 432kB Green.jpg - 1.4MB Cyan.jpg - 1.4MB
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Prepic
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[*] posted on 20-8-2020 at 08:41


I think your best bet is to redissolve everything in your original beacker. Provided your HCl and H2O2 don't contain appreciable amount of any dissolved solids you can bet whats left there is some form of nickel and should still be relatively pure. In terms of the color produced I am not sure myself.
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macckone
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[*] posted on 20-8-2020 at 09:20


My guess would be some kind of oxychloride.
Iron forms a similar oxychloride with prolonged heating of the chloride with the oxide.
I can see this forming from prolonged heating with air.

If it is the oxychloride dissolving it with hydrochloric acid should regenerate the chloride.
Some hydrogen peroxide may speed the reaction.
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B(a)P
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[*] posted on 20-8-2020 at 14:32


The colour looks about right for anhydrous nickel chloride, but given the solubility it is probably not. It is probably a mixture of oxides and anhydrous chloride and other things. Try adding water and heating, if that doesn't work try more HCl and peroxide and see what happens. You should then be able to repeat and obtain nickel chloride crystals.
When you ask should you throw the beaker away did you mean the contents or the actual beaker? How hot does your hot plate get and did you have it turned all the way up? Is it borosilicate glass, looks like it from the photo? I imagine it would be fine. Wikipedia says borosilicate can withstand temperatures up to 500C.
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QuantumDot
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[*] posted on 24-8-2020 at 10:07


Quote: Originally posted by Prepic  
I think your best bet is to redissolve everything in your original beacker. Provided your HCl and H2O2 don't contain appreciable amount of any dissolved solids you can bet whats left there is some form of nickel and should still be relatively pure. In terms of the color produced I am not sure myself.

Quote: Originally posted by macckone  
My guess would be some kind of oxychloride.
Iron forms a similar oxychloride with prolonged heating of the chloride with the oxide.
I can see this forming from prolonged heating with air.

If it is the oxychloride dissolving it with hydrochloric acid should regenerate the chloride.
Some hydrogen peroxide may speed the reaction.


So redissolving everything in HCl worked fine. That's some interesting stuff on the oxychloride possibility that I hadn't considered. As a side note, DO NOT underestimate the foaming power of H2O2. Thankfully there was no spill for my tray to catch!

Quote: Originally posted by B(a)P  
The colour looks about right for anhydrous nickel chloride, but given the solubility it is probably not. It is probably a mixture of oxides and anhydrous chloride and other things. Try adding water and heating, if that doesn't work try more HCl and peroxide and see what happens. You should then be able to repeat and obtain nickel chloride crystals.
When you ask should you throw the beaker away did you mean the contents or the actual beaker? How hot does your hot plate get and did you have it turned all the way up? Is it borosilicate glass, looks like it from the photo? I imagine it would be fine. Wikipedia says borosilicate can withstand temperatures up to 500C.


It's borosilicate glassware bought from a lab supplier. My hotplate goes to 450C and I only left it for 7-8 minutes so hopefully that's within acceptable tolerances for the glass.

I've attached a photo of the crystals formed after a more gentle evaporation in a pyrex dish in the sunlight for 2 days. I think stopping the evap by scraping up the crystals and bottling them before they had a chance to dry out to yellow helped to make a more photogenic material. I even managed to make some very pretty hexamminenickel(II) chloride with this run. There's a little hydroxide contamination thanks to unreacted nickel making it all the way through. I think next I'll redissolve the NiCl2 in water and filter it to remove the unreacted metal. (Although ammonia solution seems to dissolve the hydroxide?)

Thank you everyone for your help.



nickel chloride.png - 834kB hexamminenickel chloride.png - 948kB
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macckone
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[*] posted on 24-8-2020 at 15:25


Beautiful.
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DraconicAcid
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[*] posted on 24-8-2020 at 15:28


Aqueous ammonia will dissolve most nickel salts, including low-solubility ones like the hydroxide.



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woelen
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[*] posted on 26-8-2020 at 04:38


Indeed, the hexamminenickel(II) complex forms soluble salts with most anions. It is a very nice blue/purple complex.

Surprisingly, there is one salt of the hexamminenickel(II) complex which is not soluble in water. That is Ni(NH3)6(ClO4)2. This actually can be used as a sensitive test for nickel(II). Add a little of a soluble perchlorate salt to the solution (e.g. NH4ClO4 or NaClO4) and then add some ammonia. If there is nickel present, then you get a purple/blue precipitate of hexamminenickel(II) perchlorate.




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Antiswat
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[*] posted on 16-9-2020 at 07:12


i just want to add an warning to messing around with nickel salts, i got a nasty tremor lasting me about 24H one time i tried to seperate stainless steel apart using oxalic acid, and this happened by just spending too many minutes near a pot of insoluble nickel compound in water while the water was boiling off gently, with ventilation on.



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https://en.wikipedia.org/wiki/Solubility_table
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MidLifeChemist
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[*] posted on 17-9-2020 at 05:25


Quantum Dot, thanks for posting. This is the kind of chemistry that I like to do.

I'm sure it's simple, but would you mind outlining the exact steps you went through to produce the hexamminenickel(II) chloride, including how you dried it out? I have some NiSO4 and I'd love to try that out sometime.
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